Supplement science

Which supplements have real evidence, which are marketing and how to use them safely.

Before supplementing: the order of priorities

There is a non-negotiable hierarchy: optimal training, rest, a complete diet and hydration come before any supplement. No supplement makes up for failures in those four pillars, so it only makes sense to ask about supplements once you have those sorted. For each specific supplement, ask yourself whether it is necessary (is there a real deficiency?), effective (solid evidence?), safe and legal.

How to apply it

• Check your training, sleep, diet and hydration before spending on supplements
• Be suspicious of any supplement that promises to make up for a poor foundation

How to classify a supplement by its evidence

The ISSN (International Society of Sports Nutrition) classifies supplements into categories: A (safe, effective, solid evidence: creatine, caffeine, beta-alanine, protein, nitrates), B (mixed or promising evidence: HMB, citrulline, omega-3, vitamin D, ashwagandha) and C/D (insufficient evidence or carrying risk: glutamine for performance, most 'fat burners'). Knowing this classification saves you money and disappointment.

How to apply it

• Focus your supplement spending on category A: those are the ones that genuinely work
• Be especially sceptical of anything in category C or D sold as miraculous

Protein powder: when it makes sense

Protein powder is nothing more than a convenient way to reach your daily protein (1.6–2.2 g/kg) when food alone is not enough. Whey digests quickly and is high in leucine (ideal around training); casein digests slowly and is useful before bed; plant blends (pea+rice) match whey for protein synthesis if you adjust the dose 25–30% higher. The threshold that maximally activates muscle synthesis is around 2.5–3 g of leucine per serving (~25–30 g of whey or ~170 g of chicken).

How to apply it

• Use protein powder only to close the gap between what you eat and what you need, not as a meal replacement
• If you are vegan, raise your plant protein dose by 25–30% or combine sources to match the leucine threshold

Creatine: the most supported supplement there is

With over 500 human studies, creatine monohydrate is the supplement with the strongest evidence in all of sports science: it raises maximal strength by ~8% on average versus placebo. It works by regenerating ATP faster during intense efforts and also by retaining some intramuscular water (an anabolic signal), with no evidence of kidney damage in healthy people. No 'improved' form (HCl, buffered, etc.) has been shown to be superior to classic monohydrate.

How to apply it

• Take 3–5 g/day of creatine monohydrate indefinitely; there is no need to cycle it
• Do not pay more for 'premium' forms: monohydrate is still the reference
• Take it with carbohydrate or protein: insulin helps it enter the muscle

Caffeine: how to use it well

Caffeine blocks adenosine receptors, reducing your perception of effort and improving endurance, strength and power (+3–7% across different tests). The effective dose is 3–6 mg/kg taken 45–60 min before training; more does not improve the effect but does increase side effects. Your CYP1A2 gene determines whether you metabolise caffeine fast or slow, and daily use builds a tolerance that reverses in 1–2 weeks without it.

How to apply it

• Use 3–6 mg/kg about 45–60 min before training, no more
• If you notice it doing less and less, try a week without caffeine to reset your sensitivity
• Avoid taking it after mid-afternoon: its half-life is 5–6 h and it can steal your sleep

Beta-alanine and nitrates: the lesser-known ones with real evidence

Beta-alanine raises muscle carnosine (an acidity buffer) and improves performance in efforts of 1–4 minutes by ~2.9%; its typical side effect is a harmless tingling that is reduced with smaller, split doses. Nitrates (beetroot) improve oxygen efficiency and endurance performance, but an antiseptic mouthwash before taking them removes the effect entirely by killing the oral bacteria that activate them.

How to apply it

• Beta-alanine: 3.2–6.4 g/day split up, for at least 4 weeks before you notice the effect
• Nitrates: take beetroot juice 2–3 h before competing or training hard, and avoid antiseptic mouthwash that day

Iron: the most common deficiency in athletes

Iron deficiency (with or without anaemia) is the most frequent nutritional deficiency in athletes, especially in women who run and menstruate, and it worsens aerobic performance even before anaemia appears. Intense exercise also impairs iron absorption in the hours afterwards (via hepcidin), so supplemental iron is best taken at rest, away from training.

How to apply it

• Do not supplement iron without blood work (ferritin) confirming a deficiency: excess is also harmful
• If you suspect fatigue from low iron (especially if you menstruate or are vegan), ask for ferritin at your next blood test

Thermogenics and 'fat burners': why almost none really work

Most thermogenics (green tea, synephrine, capsaicin, L-carnitine) have real but very small effects (equivalent to tens of kcal/day), nothing comparable to adjusting your diet. Worse still: International Olympic Committee studies have found that 10–25% of commercial supplements (especially 'fat burners' and pre-workouts) contain substances not declared on the label, including unauthorised stimulants linked to real cases of heart attack and sudden death.

How to apply it

• Do not expect any 'fat burner' to replace a calorie deficit: at best it is a minimal nudge
• If you compete or simply want safety, use only supplements with third-party certification (Informed Sport, NSF Certified for Sport)

The 30-minute 'anabolic window' does not exist as we thought

For years people insisted on eating protein within 30 minutes after training or 'losing' the muscle gain. Current evidence shows that window is much wider (hours, not minutes) and that, if your total daily protein is already adequate, exact timing adds little. Timing does matter in specific cases: training fasted, doing several sessions in one day, or taking 40 g of casein before bed to sustain muscle synthesis overnight.

How to apply it

• Do not stress about eating protein 'on time': what matters is your daily total
• If you train fasted or twice a day, then it is worth managing protein and carbohydrate timing

How to choose safely

Before buying any supplement, ask yourself whether there is real evidence (ISSN category A/B), whether the manufacturer certifies purity through an independent third party, and whether the 'premium' price is justified by anything beyond marketing (as with alternative creatine forms, which do not beat monohydrate). Attractive labelling and testimonials are not evidence.

How to apply it

• Prioritise brands with third-party certification, especially if you compete
• Faced with two similar products, choose the cheaper one if both have the same evidence behind them: paying more is not paying better